The present invention generally relates to the field of rotational position sensors, and more specifically to a magnetic rotational position sensor for sensing each rotational position of a control shaft about a rotational axis over a definable range of rotation.
Electronic fuel injected engines used in motor vehicles typically embody a microprocessor based control system. Fuel is metered or injector activation time is varied in accordance with various engine parameters including the regulation of air flow into the engine via a rotational position of a throttle diaphragm relative to a closed position of the throttle diaphragm. Typically, a shaft is adjoined to the throttle diaphragm to synchronously rotate the throttle diaphragm as the shaft is rotated between the closed position and a maximal open position of the throttle diaphragm. Rotational position sensors are adjoined to the shaft to sense each rotational position of the shaft, i.e. each degree of rotation of the shaft relative to the closed position, whereby the rotational position of the throttle diaphragm relative to the closed position is sensed.
One of the problems associated with the prior magnetic rotational position sensors is magnetic hysteresis. Magnetic hysteresis causes an offset error signal to be generated whenever a magnetic element of the sensor, e.g. a magnetic pole piece or a magnetic rotor, is advanced from and returned to a reference position of the magnetic element. Annealing the magnetic element can minimize, but never eliminate, magnetic hysteresis. What is therefore needed is a novel and unique magnetic rotational position sensor that does not experience magnetic hysteresis.
The present invention overcomes the aforementioned drawback associated with prior magnetic rotational position sensors. Various aspects of the present invention are novel, non-obvious, and provide various advantages. While the actual nature of the present invention described in detail herein can only be determined with reference to the claims appended hereto, certain features which are characteristic of the present invention disclosed herein can be described briefly.
In one aspect of the present invention, a magnetic rotational position sensor comprises a loop pole piece, a magnet, and a magnetic flux sensor. The loop pole piece has an inner diameter surface defining an air gap area. The magnet disposed is in the air gap area with a first pole surface facing and spaced from the inner diameter surface and a second pole surface facing the inner diameter surface to generate a magnetic field within the air gap area and to enclose said magnetic field within the loop pole piece. The loop pole piece and the magnet are synchronously rotatable about an axis over a definable range of rotation. The magnetic flux sensor is operable to sense a magnitude of magnetic flux density passing through the magnetic flux sensor. The magnetic flux sensor is disposed within the magnetic field to sense a different magnitude of magnetic flux density passing through the magnetic flux sensor for each degree of synchronous rotation of the loop pole piece and the magnet about the axis over the definable range of rotation.
In a second aspect of the present invention, the magnetic rotational position sensor further comprises a drive circuit including a voltage divider and a current amplifier. The voltage divider is operable to provide a voltage reference signal. The current amplifier is operable to provide a current drive signal and a voltage drive signal in response to the voltage reference signal.
In a third aspect of the present invention, the magnetic rotational position sensor further comprises an output signal amplifier comprising a buffer amplifier, a voltage divider, and a differential amplifier. The buffer amplifier is operable to counteract any temperature drift of a pair of voltage sensing signals from the magnetic flux sensor. The voltage divider is operable to provide a voltage reference signal. The differential amplifier is operable to provide a voltage output signal in response to the voltage sensing signals as provided by the buffer amplifier, and the voltage reference signal.
It is a first object of the present invention to sense each rotational position of a control shaft about a rotational axis over a definable range of rotation without experiencing magnetic hysteresis.
It is a second object of the present invention to linearly sense each rotational position of a control shaft about a rotational axis over a significant scope of a definable range of rotation without experiencing magnetic hysteresis.
It is a third object of the present invention to generate one or more voltage sensing signals representative of a sensing of each rotational position of a control shaft about a rotational axis over a definable range of rotation without experiencing magnetic hysteresis.
It is a fourth object of the present invention to linearly generate one or more voltage sensing signals representative of a sensing of each rotational position of a control shaft about a rotational axis over a significant scope of a definable range of rotation without experiencing magnetic hysteresis.
It is a fifth object of the present invention to generate a voltage output signal representative of a sensing of each rotational position of a control shaft about a rotational axis over a definable range of rotation without experiencing magnetic hysteresis.
It is a sixth object of the present invention to linearly generate a voltage output signal representative of a sensing of each rotational position of a control shaft about a rotational axis over a significant scope of a definable range of rotation without experiencing magnetic hysteresis.
These and advantages of the present invention will become more apparent from the following description of the preferred embodiment.